The present invention relates to an optical detection system for a tennis court to display out-of-bounds shots and fault and let services of a tennis ball.
As even the most inexperienced tennis novice can attest, many tennis shots fall in marginal areas where it is difficult for the players or line judges to determine with any accuracy the position of the tennis ball as it strikes the playing surface. As a result, during the course of a game, several erroneous decisions can be made. In today's present surge of professional tennis with relatively high monetary awards at stake, there exists a need for more accurate judging of the game.
Several proposals have been made to automatically detect tennis balls near the line. These include the embedding of pressure-sensitive devices along the lines of the tennis court to detect the impact of the tennis ball as well as a recent proposal whereby an electromagnetic radiation system including transmission lines embedded in the court have been attempted. The latter proposal is the subject of U.S. Pat. No. 3,774,194, issued on Nov. 11, 1973 to P. Jokay et al.
While these systems represent an improvement over the present judging system, they rely either on impact caused by the tennis ball with the playing surface or on specially modified tennis balls which interact with the electromagnetic field around the court. As a result, the installation requires the embedding of wires in the tennis court and is of a permanent nature requiring installation when the tennis court is initially constructed or relatively expensive modification to existing courts. Such systems, once installed, therefore, cannot be employed in other courts and should they require repair, it may be necessary to tear up the boundary lines of the court to obtain access to a broken wire or other buried component.
If a simple single beam optical detector were employed with a beam tracing the boundaries, the beam could be interrupted by either a tennis ball or one of the players' feet. Thus, such a system would not be reliable in detecting out-of-bounds shots.
There exists, therefore, a need for a system which provides the desired accuracy to at least assist the judges in making close calls and one which is relatively simple and thus, inexpensive to manufacture and maintain. Preferably, this system should be portable such that it can be employed at different locations and be easily repaired.